Anaesthetic apparatus

ABSTRACT

The present invention relates to an apparatus for delivering an anaesthetic to human or animal patients. The apparatus comprises an anaesthetic machine which is arranged to mount components of an anaesthetic delivery circuit, and which includes a collector arrangement in the form of a manifold ( 21 ) having a plurality of inlets and outlets. The manifold ( 21 ) enables a reduction in the number of tubes connecting the various components in an anaesthetic system, which are normally required in prior art anaesthetic machines. The manifold ( 21 ) also includes an arrangement ( 40 ) which provides a Venturi effect on gas flow, and enables a pressure gauge ( 18 ) to be mounted out of a patient breathing circuit. The machine is preferably portable.

FIELD OF INVENTION

[0001] The present invention relates generally to an apparatus fordelivering anaesthetic to a human or animal patient, and in particularto an anaesthetic apparatus facilitating the delivery of inhalationanaesthetics.

BACKGROUND OF INVENTION

[0002] Inhalation anaesthetics are drugs that are breathed into thelungs and from there absorbed into the blood. Inhalation anaestheticsare either gases (such as nitrous oxide, helium, etc) or vapours.Vapours are usually produced by volatile liquids, which primarily existas a liquid at room temperature. Inhalation anaesthetic agents that arevapours include halothane, isoflurane, enflurane and sivoflurane.

[0003] To facilitate administration of anaesthetic vapours, it isusually necessary to encourage the liquid to form a vapour or gas. Thisvapour is administered in a controlled fashion to an anaestheticbreathing circuit, and therefore to the patient. The devices which holdthe liquid anaesthetic and produce a vapour are called anaestheticvaporisers. Anaesthetic vapour is collected from the vaporiser anddelivered to the anaesthetic breathing circuit using oxygen, which isrequired to sustain the life of the patient. The oxygen flows throughthe anaesthetic vaporiser and carries the vapour to the anaestheticbreathing circuit.

[0004] Anaesthetic vaporisers must perform predictably and must becapable of delivering accurate, controlled dosages of anaesthetic vapourto the anaesthetic breathing circuit. For example, the anaesthetic doseof halothane which is administered to the lungs is between 1% and 2%.The lethal dose of halothane is around 3%-4%. It is therefore importantthat anaesthetic vaporisers are maintained and not subject to conditionswhich may damage them and render their output inaccurate.

[0005] Anaesthetic circuits vary in type. The aim is to deliver acontrolled amount of anaesthetic and oxygen to a patient. Circuitsinclude “rebreathing” systems which contain valves and soda lime (whichremoves the carbon-dioxide exhaled by the patient, so that the exhaledgas can be re-breathed) or non-rebreathing systems which have nosoda-lime and where all exhaled gases are exhausted (eg T pieces, Baincircuits, Norman elbows).

[0006] Any anaesthetic delivery system will usually include a number ofelements, as follows:

[0007] Oxygen supply, usually in the form of a pressurised vessel, witha regulator, for providing oxygen to the anaesthetic system; an oxygenflow meter for monitoring oxygen flows; a vaporiser connected in theoxygen flow line providing anaesthetic to the anaesthetic breathingcircuit; an oxygen flush valve and lines to bypass the vaporiser toprovide pure oxygen to the patient without anaesthetic; a pressure gaugeto indicate the pressure in the patient's breathing circuit; various gaslines connecting together all the components in the circuit.

[0008] Some or all of these components may be mounted to a supportstructure, forming what is known as an anaesthetic machines. Thissupport may provide mountings for the flow meter, the vaporiser and alsomountings for the various gas lines connecting the anaesthetic deliverysystem. Anaesthetic machines tend to be of two types. A first type arelarge machines mounted on four wheel trolleys, usually with allcomponents enclosed, and typically found in hospital surgeries. A secondtype is small machines which are portable and can be hand carried orfitted to a small mobile stand. One problem with present arrangements ofportable anaesthetic machines is that because there are a number ofrelatively long gas flow lines, many of which remain exposed, they couldbecome tangled and could even be pulled out during operation ortransport of the system. This is dangerous. Further, any anaestheticmachine which has exposed gas lines is difficult to transport either toend user or between hospitals or after sale service of machine (eg tothe end user after sale or service of the machine) without damage, aswell as being inconvenient to use.

SUMMARY OF INVENTION

[0009] The present invention provides, from a first aspect, a connectorarrangement for an anaesthetic delivery system, the connectorarrangement comprising a manifold including at least one inlet and aplurality of outlets, the at least one inlet and the plurality ofoutlets being arranged for connection to gas lines in the anaestheticcircuit, whereby the manifold facilitates minimising the extent of gasline components required in the anaesthetic circuit.

[0010] The manifold preferably comprises a plurality of inlets.Preferably, the manifold includes a first, high pressure portion,including an oxygen inlet for receiving oxygen from an oxygen supply andregulator, and an oxygen outlet for providing oxygen to an oxygen flowmeter, and a second, low pressure portion, having a vaporiser inlet forreceiving oxygen and anaesthetic from the vaporiser and a patient outletfor providing oxygen/anaesthetic mixture to a patient breathing circuit.

[0011] Provision of such a manifold preferably enables the reduction ofthe extent of gas lines and complexity of gas line connection componentsover prior art anaesthetic systems and preferably enables the provisionof an anaesthetic machine incorporating the manifold in which there areno exposed gas lines or the exposure of gas lines is minimised, and thecomplexity of servicing is reduced as the extent of connecting gas linesis reduced.

[0012] The connector arrangement of the present invention may be usedwith either type (portable or non-portable) anaesthetic machine, but hasparticular advantage in use with the portable machine. It advantageouslyfacilitates the production of a portable machine which can be used inveterinary surgery applications, and also a portable machine which canbe used for human anaesthesia applications, e.g. which may be used on anambulance or which may have military (field hospital) applications.

[0013] Preferably, the manifold is an integrated body incorporatingconduits connecting the inlets and outlets. The manifold therefore,preferably provides a single body which effectively replaces multiplecomponents connecting gas lines in prior art anaesthetic supplycircuits.

[0014] Preferably, an oxygen flush outlet is provided in the manifoldfor connection to a flush valve and an oxygen flush inlet is providedfor connection from the flush valve, thereby providing a flush bypassline, for oxygen to be provided directly to the patient outlet andthereby to the patient, bypassing the vaporiser.

[0015] A further problem with prior art anaesthetic supply circuits isthe possibility of causing damage to the anaesthetic vaporiser when theflush valve is operated to bypass the vaporiser and provide oxygendirectly to the patient. Because oxygen is provided directly from thehigh pressure end of the circuit in this case (ie from a line connectedto the regulator and oxygen supply tank), high pressure oxygen caninadvertently flow back along the vaporiser patient line to the outletof the vaporiser, affecting vaporiser performance and sometimes causingdamage. As anaesthetic vaporisers are very delicate and performance andaccuracy is important, even minor back pressure can alter performancedamage can cause major problems (inaccurate vaporiser can cause accidentand even death).

[0016] Preferably, the manifold includes in the low pressure portionconnected to the oxygen flush inlet a Venturi arrangement, preferably inthe form of a “Venturi” injection orifice, the injection orifice beingplaced adjacent to a conduit connected to the vaporiser inlet, whereby aVenturi effect occurs, maintaining relatively low pressure in theconduit from the vaporizer inlet.

[0017] Preferably, therefore, when the flush valve is operated, theVenturi effect provided by the Venturi injection orifice in its positionwith respect to the vaporiser inlet, maintains relatively low pressurein the line back to the outlet of the vaporiser. There is thereforepreferably no flow of a relatively high pressure oxygen to the outlet ofthe vaporiser during flush operation, and therefore no back pressureeffect or damage to the vaporiser.

[0018] The Venturi arrangement also preferably enables a pressure gaugefor monitoring the pressure of the patient's breathing circuit to bemounted outside the breathing circuit and be connected to the vaporiserinlet of the manifold. Normally, it is necessary to mount the pressuregauge in the patient breathing circuit, to avoid the possibility ofdamage on operation of the flush valve. The Venturi arrangementpreferably dispenses with this need and the pressure gauge can bemounted out of the patient breathing circuit. This has the advantagethat a single pressure gauge can be used for both rebreathing andnon-rebreathing patient breathing circuits, whereas in the prior art itis usually necessary to use separate pressure gauges.

[0019] In a preferred embodiment of the present invention, the vaporiserincludes a universal outlet on which the pressure gauge is directlymounted.

[0020] Preferably, the manifold also includes an additional oxygenoutlet, which can be used for providing oxygen from the line from theregulator and oxygen tank, to an additional flow meter for an additionalpatient breathing circuit or to an anaesthetic ventilator. This featurewould be particularly advantageous in a small or temporary clinicfacility where oxygen may not be piped to every bedside. This can enablethe same anaesthetic system to be used for two patients as could, forexample, occur during a caesarean section when the mother is breathingfrom the anaesthetic circuit and the infant might require oxygen via ega face mask immediately after delivery.

[0021] Anaesthetic machine design and standardisation has resulted in avariety of breathing circuit designs and connectors being available indifferent countries. Preferably, the patient outlet is formed as a“universal” outlet which allows connection of a plurality of standardconnectors.

[0022] The present invention further provides, from a second aspect, ananaesthetic machine comprising a housing including means for mountingcomponents of an anaesthetic delivery system, and including a connectorarrangement in accordance with the preceding aspect of the inventiondiscussed above.

[0023] Because of the provision of the connector arrangement in theanaesthetic machine, the extent of gas lines required can preferably beminimised.

[0024] The present invention yet further provides, from a third aspect,an anaesthetic machine comprising a housing, including means formounting components of an anaesthetic delivery system, the housingcomprising a base, a back wall and a top wall extending over the base,the base, back wall and top wall forming an enclosure and the means formounting the components being within the enclosure, whereby any gaslines required to connect the components mounted in the enclosure runwithin the enclosure.

[0025] Preferably therefore, the enclosure operates to protectcomponents and gas lines connecting the component from accidentaldamage.

[0026] Preferably, a connector arrangement in accordance with the firstaspect of the invention is mounted within the enclosure.

[0027] Preferably, an anaesthetic machine of the second aspect of theinvention discussed above also includes a housing forming an enclosurein accordance with the third aspect of the invention discussed above.

[0028] Preferably, in both the second and third aspects of theinvention, the means for mounting includes means for mounting avaporiser within the enclosure, and also preferably a flow meter withinthe enclosure.

[0029] Preferably, the wrap around top shelf enables the manifold to bemounted in an elevated position, to facilitate attachment of patientcircuits where the breathing tubes and other components may need to beelevated. Note that the present apparatus can be used with any type ofcircuit and is not limited to the patient circuits illustrated in thedrawings and described in the description.

[0030] Preferably, the anaesthetic machine also includes means formounting a pressure gauge, which is preferably mounted out of thepatient breathing circuit, as discussed in relation to the first aspectof the invention discussed above.

[0031] The present invention yet further provides, in an anaestheticdelivery system comprising a vaporiser connectable to an oxygen supplyand a patient breathing circuit, for providing a mixture of oxygen andanaesthetic to the patient breathing circuit, and a flush bypass systemfor bypassing the vaporiser to provide oxygen directly to the patientbreathing circuit, a method of avoiding relatively high pressure oxygenbeing provided back to the vaporiser from the flush bypass system onoperation of the flush bypass system, comprising the step of employingthe Venturi effect to maintain relatively low pressure in a line fromthe vaporiser to a connection with the flush bypass system.

[0032] The present invention further provides, in an anaestheticdelivery system comprising a vaporiser connectable to an oxygen supplyand a patient breathing circuit, for providing a mixture of oxygen andanaesthetic to the patient breathing circuit, and a flush bypass systemfor bypassing the vaporiser to provide oxygen directly to the patientbreathing circuit, an arrangement for avoiding relatively high pressureoxygen being provided back to the vaporiser from the flush bypass systemon operation of the flush bypass system, comprising at a connectionbetween a line from the vaporiser and the flush bypass system, a Venturiarrangement which, when the flush bypass is actuated, operates tomaintain relatively low pressure in a line from the vaporiser,substantially avoiding high pressure oxygen flowing into that line andback to the vaporiser.

[0033] With the above arrangement, preferably the anaesthetic deliverysystem also includes a pressure gauge, which is preferably mounted outof the patient's breathing circuit and preferably connected to the linebetween the vaporiser and the flush bypass system.

[0034] Preferably, the pressure gauge is mounted directly to thevaporiser outlet, preferably via a universal connector.

BRIEF DESCRIPTION OF DRAWINGS

[0035] Features and advantages of the present invention will becomeapparent from the following description of an embodiment thereof, by wayof example only, with reference to the accompanying drawings, in which,

[0036]FIG. 1 is a schematic diagram illustrating a prior art anaestheticdelivery system;

[0037]FIG. 2 is a schematic diagram illustrating an anaesthetic deliverysystem employing a connector arrangement in accordance with anembodiment of the present invention;

[0038]FIG. 3 is a perspective view of a connector arrangement inaccordance with an embodiment of the present invention, internalstructural features being shown in ghost outline;

[0039]FIG. 4 is a perspective view from the front of an anaestheticmachine in accordance with an embodiment of the present invention;

[0040]FIG. 5 is a perspective view from the front of the anaestheticmachine of FIG. 4, shown connected to a patient rebreathing circuit;

[0041]FIG. 6 is a perspective view from the front of the anaestheticmachine of FIG. 4 shown connected to a patient non-rebreathing circuit;

[0042]FIG. 7 is a perspective view from the front of the anaestheticmachine of FIG. 4 illustrating use of an additional flow meter, and

[0043]FIG. 8 is a perspective view from the front of an anaestheticmachine in accordance with a further embodiment of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0044] Referring to FIG. 1, a prior art anaesthetic delivery system isillustrated. The delivery system includes a pressurised source 1 ofoxygen, a regulator 2 for regulating the supply of oxygen from thesource 1 and a pressure gauge 3 for monitoring oxygen pressure.Flowmeter 4 is connected in a line 5 from the regulator 2 to ananaesthetic vaporiser 6. Anaesthetic vaporiser 6 may be of any knowntype which can provide anaesthetic vapour to the anaesthetic supplysystem. The gas line 7 connects the outlet 8 of the vaporiser 6 to apatient circuit designated generally by a reference numeral 9 which, inthis case, is a rebreathing type circuit. The rebreathing circuit 9comprises a gas line 10 providing anaesthetic oxygen mixture to a line11 to the patient. A mask or endotracheal tube (not shown) will usuallybe connected to the line 11 in order to delivery the anaesthetic oxygenmixture to the patient. A return line 12 receives waste gases from thepatient. These are conveyed via vessel 13 which contains soda lime forremoving carbon dioxide from the waste gases so that the gases can berebreathed. Non return valves 14, 15 ensure that gas flow direction inthe rebreathing circuit 9 is one way. The rebreathing circuit 9 alsoincludes a reservoir or rebreathing bag 16 which provides a variablestorage volume to compensate for variations in sizes of breath for eachpatient. It also allows for positive ventilation. A “pop-off” valve 17is also provided for relieving pressure in the circuit if necessary. Apressure gauge 18 is provided to indicate the pressure in the patientrebreathing circuit 9. A flush bypass system, in this example,comprising a bypass line 19 and flush valve 20, is provided to bypassthe vaporiser 6 and provide pure oxygen to the circuit 9 on operation ofthe flush valve 20.

[0045] This prior art circuit has the problems which are discussed inthe preamble of this specification. These include the fact (in portablemachines, in particular) that the lines 19, 5, 6, usually exposed, caneasily get in the way and become damaged and tangled. Operation of theflush valve 20 can lead to high pressure oxygen being provided to theoutlet 8 of the vaporiser causing damage to the delicate components ofthe vaporiser.

[0046] Referring to FIGS. 2 and 3, a description will now be given of ananaesthetic supply system incorporating a connector arrangement inaccordance with an embodiment of the present invention. The samereference numerals in FIG. 2 designate the same features as the supplycircuit of FIG. 1, and no further description will be given of thesefeatures.

[0047] The anaesthetic supply system illustrated in FIG. 2, utilises aconnector arrangement in accordance with an embodiment of the presentinvention, which in this example, comprises an integral cast and workedmetal manifold 21. The manifold 21 has a plurality of inlets and outletsfor connection to gas lines in the anaesthetic supply system.

[0048] In FIG. 3, the manifold 21 is essentially divided into twoportions. These include a high pressure portion 22 for connection to gaslines at a high pressure end of the anaesthetic supply system, and a lowpressure portion 23 for connection to gas lines of a low pressure end ofthe anaesthetic supply circuit.

[0049] At the high pressure portion 22, there is an oxygen inlet port 24for receiving oxygen from gas line 26 leading from the regulator 2. Anoxygen outlet 27 outlets oxygen to line 28 and the flowmeter 4. Theoxygen inlet 24 and oxygen outlet 27 are connected by conduits 29, shownin ghost outline. In addition a oxygen flush outlet 30 connects to aline 31 and to oxygen flush valve 20 (FIG. 2). An additional oxygenoutlet 32 connects to a line 33 and an additional flowmeter 34. Theadditional flowmeter can be used if it is required to provide oxygen toa second patient, eg a new-born infant.

[0050] In FIG. 3, the low pressure end 23, there is provided a oxygenflush inlet 35 connecting to line 36 from the flush valve 20. There isalso provided a vaporiser inlet 37 for connection to the line 38 fromthe vaporiser 6, and a patient outlet 39 to deliver gases to the patientbreathing circuit 9.

[0051] The provision of the manifold 21 in the anaesthetic supply systemreduces the extent of gas lines required over the prior art supplysystem and allows the arrangement to be organised in a much “tidier”manner which facilitates installation service and shipping.

[0052] As discussed in the preamble, one of the problems in operation ofthe flush valve 20 in the prior art supply system (FIG. 1) is thatrelatively high pressure oxygen directly from the regulator 2 can beprovided back to the outlet 8 of the vaporiser 6, resulting in damage tothe vaporiser. The low pressure end 23 of the manifold 21 (FIG. 3)provides a Venturi arrangement 40 which, in this case, includes aninjection orifice 41 connecting to a conduit 42 which connects to theoxygen flush inlet port 35. Injection orifice 41 opens into a broaderconduit 43 leading to the patient outlet 39. A conduit 44 from thevaporiser inlet opens into the side of the conduit 43, substantiallyperpendicular to the flow from the injection orifice 41. In operation,when the flush valve 20 is operated, relatively high pressure oxygenintroduced to the oxygen flush inlet 35 is ejected from the injectionorifice 41 in a direction across the face of the internal opening of theconduit 44 into the conduit 43. This creates a Venturi effect, whichresults in the reduction of the pressure in line 38 between thevaporiser and the vaporiser inlet 37. This reduces the possibility ofhigh pressure oxygen from the flush system being forced back to theoutlet of the vaporiser 8.

[0053] Further, in the prior art anaesthetic supply circuits, it isusually necessary to place the pressure gauge in the patient breathingcircuit with the present arrangement (FIG. 2), however, the pressuregauge 18 can be placed in the line 38 between the vaporiser and thevaporiser inlet 37. The reason for, in the prior art, placing thepressure gauge 18 in the patient breathing circuit is that there is achance of damage due to high pressure oxygen flow on operation of theflush system. As the possibility of flow into line 38 is reduced becauseof the Venturi arrangement 40, this means that a pressure gauge 18 canbe placed out of the patient breathing circuit as indicated in FIG. 2.This has the advantage that a single pressure gauge can be available forany type of patient breathing circuit, eg rebreathing, non-rebreathing.It is not necessary to provide a pressure gauge separately.

[0054] At the patient outlet 39 of a manifold 21 (FIG. 3), a universaloutlet connector 45 is provided, for connecting to line 7 to the patientbreathing circuit. Anaesthetic machine design has resulted in thestandardisation of a variety of breathing circuit components andconnectors. The universal outlet 45 includes a 15 mm internal diameterportion, seven eighths of an inch outside diameter portion and 23 mmoutside diameter portion to take these three standard connectors.

[0055] Referring to FIG. 4, an anaesthetic machine in accordance with anembodiment to the present invention will now be described.

[0056]FIG. 4, the same reference numerals are used for components whichhave already been described in relation to FIGS. 1 and 3.

[0057]FIG. 4 discloses an “anaesthetic machine” which includes a housingincluding means for mounting components of an anaesthetic supply system.In this embodiment, the housing includes a support 50, comprising a base51, a back wall 52 and a top wall 53. The base 51, back wall 52 and topwall 53 form an enclosure within which components of the anaestheticsupply system, including vaporiser 6, pressure gauge 18, flowmeter 4 andalso gas flow lines 20, 38, 31, 36 and flush valve 20 are mounted,substantially shielded from the external environment. The support 50thus protects important components and gas lines from accidental damage.In the illustrated embodiment, a manifold 21 as described above withreference to FIGS. 1 to 3 is mounted to the top wall 53 of the support50.

[0058] It will be appreciated that the anaesthetic machine could be usedwithout the manifold, but still protecting gas lines within theenclosure provided by the support 50. It is preferred, however, that themanifold 21 be utilised.

[0059] The “enclosed” design of the anaesthetic machine enables themachine body to be fully assembled, including vaporiser, ready for useupon removal from packaging with minimal risk of damage during shipment(all delicate components being located within the enclosure). Theelimination of exposed high pressure oxygen lines to the flowmeter,oxygen flush valve etc minimises potential damage during shipment or inuse (in prior art portable machines these lines are located in anexposed position at the back of the machine).

[0060] An additional advantage of the support 50 is that the top wall 53provides a top surface which can be used as a work surface and it alsoacts as an elevated shelf for monitoring equipment to increase thevisibility of the display.

[0061] An intravenous infusion pole 54 is attached at the back of themachine and the machine is supported upon a movable trolley 55. Anadditional flowmeter 34 is mounted to the top wall 53. A mount 56 for apatient breathing circuit is fixed within the enclosure supported on thebase 51.

[0062]FIG. 5 shows the machine of FIG. 4 connected to a patientrebreathing circuit 9. Again reference numerals used are the same as forcorresponding components shown in the other figures, and no furtherdescription will be given for the rebreathing circuit.

[0063]FIG. 6 illustrates the anaesthetic machine of FIG. 4 connected toa patient non-rebreathing system 60. The non-rebreathing system 60includes a gas line 61 from the manifold 21 to a non-rebreathing line 23to a patient port 24 for providing anaesthetic and oxygen to a patient.The non-rebreathing system 60 also includes a reservoir bag 65 and exitport 66 for exiting waste gases.

[0064]FIG. 7 shows use of the additional flowmeter 34 via anon-rebreathing system. Pure oxygen can be provided by the additionalflowmeter 34 to ventilate additional patients, eg. newborn infants.

[0065] A preferred embodiment of an anaesthetic machine in accordancewith the present invention is illustrated in FIG. 8. Correspondingcomponents are given the same reference numerals as in previousdrawings. In this embodiment, the pressure gauge 18 is connecteddirectly to the outlet 8 of the vaporiser. The outlet 8 of the vaporiseris formed as a universal vaporiser outlet which includes a connection 61for the pressure gauge.

[0066] In the embodiment described above the manifold 21 is shown as asingle, integrated block. An extra arrangement could, for example,comprise two separate pieces, eg. a high pressure portion and a lowpressure portion.

[0067] Note that the manifold need not be made of metal as in the aboveembodiment, but can be made of any suitable material.

[0068] Note that the Venturi effect need not necessarily be provided bythe manifold, as described in the above embodiment.

[0069] Where the Venturi effect is required, it may be applied by amanifold with the structure discussed above, or by other apparatus.

[0070] Variations and/or modifications may be made to the invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The preferred embodimentsare, therefore, to be considered in all respects as illustrative andnon-restrictive.

The claims defining the invention are as follows:
 1. A connectorarrangement for an anaesthetic circuit, comprising a manifold includingat least one inlet and a plurality of outlets, the at least one inletand plurality of outlets being arranged for connection to gas lines inthe anaesthetic circuit, whereby to facilitate minimising the extent ofgas line components required in the anaesthetic circuit.
 2. A connectorarrangement in accordance with claim 1, wherein the manifold comprises aplurality of inlets.
 3. A connector arrangement in accordance with claim2, wherein the manifold includes a first, high pressure portion,including an oxygen inlet for receiving oxygen from an oxygen supply andregulator, and an oxygen outlet for providing oxygen to an oxygenflowmeter, and a second low pressure portion, having a vaporiser inletfor receiving oxygen and anaesthetic from a vaporiser, and a patientoutlet for providing oxygen/anaesthetic mixture to a patient breathingcircuit.
 4. A connector arrangement in accordance with claim 3, furthercomprising a oxygen flush outlet provided for connection to a flushvalve and a oxygen flush inlet provided for connection from the flushvalve, whereby to enable the provision of a flush bypass line forenabling oxygen to be provided directly to the patient outlet andthereby to the patient, bypassing the vaporiser.
 5. A connectorarrangement in accordance with claim 4, wherein the manifold includes inthe low pressure portion connected to the oxygen flush inlet a Venturiarrangement to cause a Venturi effect to maintain a relatively lowpressure at the vaporiser inlet.
 6. A connector arrangement inaccordance with any one of claims 3 to 5, wherein the patient outletincludes a universal connector arrangement for connecting to standardpatient breathing circuit lines.
 7. A connector arrangement inaccordance with any one of claims 3 to 6, an additional oxygen outletbeing provided at the high pressure end of the manifold.
 8. Ananaesthetic delivery system incorporating a connector arrangement inaccordance with any one of claims 1 to
 7. 9. An anaesthetic deliverysystem in accordance with claim 8, including a pressure gauge mountedout of the patient breathing circuit.
 10. An anaesthetic delivery systemin accordance with claim 9 when read onto claim 8 and claim 5, whereinthe pressure gauge is connected in the line to the oxygen vaporiserinlet of the manifold.
 11. An anaesthetic machine comprising a housingincluding means for mounting components of an anaesthetic deliverysystem, and including an arrangement in accordance with any one ofclaims 1 to
 7. 12. An anaesthetic machine comprising a housing includingmeans for mounting components of an anaesthetic delivery system, thehousing comprising a base, a back wall and a top wall extending over thebase, the base, back wall and top wall forming an enclosure and themeans for mounting the components being within the enclosure, wherebyany gas lines required to connect the components mounted in theenclosure run within the enclosure.
 13. An anaesthetic machine inaccordance with claim 12, including a connector arrangement inaccordance with any one of claims 1 to
 7. 14. In an anaesthetic deliverysystem comprising a vaporiser connectable to an oxygen supply and apatient breathing circuit, for providing a mixture of oxygen andanaesthetic to the patient breathing circuit, and a flush bypass systemfor bypassing the vaporiser to provide oxygen directly to the patientbreathing circuit, a method of avoiding relatively high pressure oxygenbeing provided back to the vaporiser from the flush bypass system onoperation of the flush bypass system, comprising the step of employing aVenturi effect to maintain relatively low pressure in a line from thevaporiser to a connection with the flush bypass system.
 15. In ananaesthetic delivery system comprising a vaporiser connectable to anoxygen supply and a patient breathing circuit, for providing a mixtureof oxygen and an anaesthetic to the patient breathing circuit, and aflush bypass system for bypassing the vaporiser to provide oxygendirectly to the patient breathing circuit, an arrangement for avoidingrelatively high pressure oxygen being provided back to the vaporiserfrom the flush bypass system on operation of the flush bypass system,the arrangement comprising at a connection between a line from thevaporiser and the flush bypass system, a Venturi arrangement which, whenthe flush bypass system is actuated, operates to maintain in relativelylow pressure in the line from the vaporiser, substantially avoiding highpressure oxygen flowing into that line and back to the vaporiser.
 16. Ananaesthetic delivery system, comprising a means for delivering oxygenand anaesthetic, and a pressure gauge mounted to the means fordelivering oxygen and anaesthetic, the pressure gauge being mountedbefore a patient breathing connection.
 17. An anaesthetic deliverysystem in accordance with claim 16, wherein the means for deliveringanaesthetic and oxygen includes an anaesthetic vaporiser and wherein thepressure gauge is mounted to an outlet of the anaesthetic vaporiser.